Resonator with counterrotating rigid parts

ABSTRACT

A resonator comprising a plurality of rigid pivotable members are interconnected by a flexible member which is arranged to induce counterrotary movement of the rigid members upon driving of one of the members. In order to provide a resonator having a relatively low resonant frequency, the flexible member is relatively long and is connected to the rigid members on opposite sides of the nodal axes thereof.

0 United States Patent l l3,582,698

[72] inventor Hugh M. Baker,Jr. 2,978,597 4/1961 Harris 310/82 5005 Nebraska Ave., Washington, DC. 3,277,394 10/1966 Holt et al. 331/1 16 20008 2,696,590 12/1954 Roberts 333/71 l PP 836,026 OTHER REFERENCES 2% :f t d i 1 Baker & Cressey, H-Shaped Resonators Signal Upturn in i 1 a an e um Tone Telemetering Electronics October 2, 1967, pp 99- [54] RESONATOR WITH COUNTERROTATING RIGID Primary ExaminerD. F. Duggan PARTS Assistant Examiner-B. A. Reynolds 4 Claims, 6 Drawing Flgs- Attorney-G. Turner Moller 52 11.5. CI SIG/8.2, 310/85, 333/72 [51] Int. Cl 01v 7/00 ABSTRACT; A on tor comprising a plurality of rigid Field of Search pivotable members are interconnected a flexible member 333/72, 30, 71 which is arranged to induce counterrotary movement of the rigid members upon driving of one of the members. In order to [56] References Cited provide a resonator having a relatively low resonant frequen- UNITED STATES PATENTS cy, the flexible member is relatively long and is connected to 3,308,313 3/ 1967 Farre 310/36 the rigid members on opposite sides of the nodal axes thereof.

RESONATOR WITH COUNTERROTATING RIGID PARTS CROSS-REFERENCE TO RELATED APPLICATIONS This application is related to application Ser. No. 565,430 entitled RESONATOR TOGETHER WITH METHOD AND MEANS FOR VARYlNG THE FREQUENCY THEREOF, filed July 15, 1966, and application Scrt No. 7l4,22l entitled RESONATOR, now US. Pat. No. 3,453,464, filed Mar. I9, 1968.

BACKGROUND OF THE lNVENTlON This invention relates to resonators and filters of the electromeehanical type An electromechanical resonator is disclosed in Electronics Magazine, Oct. 2, I967, pages 99 106 which comprises a pair of rigid members arranged to pivot or rotate about the nodal axis thereof. The rigid members are interconnected by a bodily flexible member arranged to induce counterrotary movement between the rigid parts. The device disclosed in this publication is likewise disclosed and claimed in application Ser. No. 565,430 and is generally H-shaped in configuration with the flexible part or web being substantially smaller than the rigid parts.

lt has been found desirable to provide a resonator of this general type which is adapted for low-frequency operation. For example, it may be desirable to provide a 60-cycle resonator. One mode of accomplishing this desideratum is to make the flexible part or web of substantially greater length. It may be readily appreciated that the third part or web of the resonator disclosed in the aforementioned application and publication may be made of any desirable length. It will be apparent that the device a assumes substantially greater external dimensions and therefore sacrifices compactness to some extent when the web is increased in length. One approach for increasing the overall dimension of the web without increasing the external dimension of the resonator is disclosed in application Ser. No. 714,22l wherein the web is diagonally arranged between opposite ends of the rigid parts. One characteristic of the device disclosed in this application is that the web is quite flexible and is driven with very small forces. Consequently, electromagnets and very thin piezoelectric wafers are most conveniently used to drive this type of resonator. Some difficulty has been encountered in providing sufficiently thin piezoelectric wafers for this type device.

SUMMARY OF THE INVENTION In order to provide a resonator comprising counterrotating rigid parts having a relatively long web, the web or flexible part is secured to the rigid members in the plane defined by the nodal axes with both of the nodal axes being disposed between the connections ofthe web and the rigid parts.

It is accordingly an object of the invention to provide a lowfrequency compact resonator comprising a plurality of bodily rigid members arranged to rotate about the nodal axes thereof.

Another object of the invention is to provide a compact resonator capable of low-frequency operation comprising first and second bodily rigid members and a third bodily flexible member arranged to induce counterrotary movement of the first and second members upon driving ofone of the members.

Another object of the invention is to provide a resonator of increased quality or selectivity which is capable of lowfrequency operation without changing the external dimensions of the device.

Still another object of the invention is to provide a resonator having high Q and large movements of the moving parts.

Further objects, advantages and important features of the invention will be apparent from a study of the specification following taken with the drawing which together describe and disclose preferred embodiments of the invention in what is now considered and believed to be the best mode of practicing the principles thereof. Still other embodiments, modifications or equivalents may be apparent to those having the benefit of the teachings herein and such other embodiments, modifications or equivalents are intended to be reserved especially as they fall in the scope and breadth of the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of one embodiment of the invention, certain parts being omitted for purposes of clarity;

FIG. 2 is a transverse cross-sectional view of the embodiment of FIG. I taken substantially along line 2-2 thereof as viewed in the direction indicated by the arrows;

FIG. 3 is a top plan view of another embodiment of the invention;

FIGv 4 is a transverse cross-sectional view of the embodiment of FIG. 3 taken substantially along line 4 4 thereof as viewed in the direction indicated by the arrows;

FIG. 5 is a side elevational view of another embodiment of the invention illustrating a different type of connection between the flexible web and the rigid parts;

FIG. 6 is a partial sectional view of the embodiment of FIG. 5 illustrating the connection between the flexible part and the rigid part.

DETAILED DESCRIPTION OF THE EMBODIMENTS Reference is made to FIGS. 1 and 2 wherein there is shown a resonator 10 having as major components an oscillatible structure 12 comprised of first and second rigid parts 14, 16 and a flexible part 18, support means 20 and means 22 for energizing the oscillatible structure 12.

The parts l4, 16 may be described as bodily rigid or rigid by which is meant that the parts 14, 16 are unflexing at a resonant frequency of the resonator [0 a although the parts 14, 16 may flex at higher frequencies. The parts l4, 16 are illustrated as rectangular in configuration but may be of any suitable geometric shape, such as cylinders, externally threaded cylinders, externally threaded tubes, internally threaded tubes, tubes, internally and externally threaded tubes, dumbbells, cones, D-shaped segments or the like.

Although it is preferred that the parts I4, 16 be of the same geometric shape for convenience of manufacture, such is not necessary. Since the quality or Q of this type resonator is highest when the parts l4, 16 have equal mass moments of inertia, it is preferred that the mass moments of inertia be sufficiently close to provide a resonator of the quality desired for a given application. The mass moments of inertia of the parts l4, 16 may be adjusted by adjustably mounting an additional weight on the exterior of the rigid members l4, 16, by adjustably mounting an additional weight in an internal passageway in the parts l4, 16 or by a combination of both. As will be realized by those skilled in the art, the change of mass moment of inertia will produce a change in the resonant frequency of the resonator 10v The first and second parts l4, 16 are provided with an aperture or passageway 24, 26 extending through the nodal axis 28, 30 respectively of the parts l4, 16. The purpose of the passageways 24, 26 will become apparent as this description proceeds.

The support means 20 comprises a base 32 and a spaced plate 34. A set of aligned conical bearings 36, 38 and 40, 42 is provided for the rigid parts l4, l6 and enables the parts l4, 16 to rotate about the respective nodal axis 28, 30. The nodal axes 28, 30 substantially intersect the center of gravity 44, 46 of the rigid parts l4, 16. It will be apparent that any suitable bearing construction may be used.

The third part 18 is arranged to induce counterrotary movement of the first and second parts l4, l6 and is affixed thereto at first and second locations 48, 50 respectively. The third part 18 may be described as bodily flexible or flexible by which is meant that the part 18 is flexible at a resonant frequency of the parts l4, 16 even though it may be rigid at lower frequencies. The third part 18 extends through the passageways 24, 26

and may be provided with projections 52, 54 at the ends:

thereof to facilitate securement to the parts l4 16. The projections 52, 54 may be welded, soldered, glueo or otherwise secured to the parts l4, 16 in any suitable manni r.

It will be noted that the nodal axes 28, 30 define a plane in which the first and second locations 48, 50 substantially reside. It will also be seen that the nodal axes 28, 30 are located between the first and second locations 48. 50. This arrangement provides the longest web commensurate with transverse dimensions of the resonator 10. It will be apparent to those skilled in the art that the locations 48, 50 may reside between the nodal axes 28, 30 and the external edge of the rigid parts 14, 16.

The energizing means 22 preferably comprises a piezoelectric wafer 56 energized by a pair of wires 58, 60 in a conventional manner. When a voltage of given polarity is applied to the piezoelectric element 56, the element 56 expands to move the flexible part 18 into the upwardly concave configuration shown in dashed lines in FIG. 1. Because of the connection between the part 18 and the parts 14, 16, the parts 14, 16 are counterrotated about the nodal axes 28, 30 into the upwardly converging attitude shown in dashed lines in FIG. 1.Whcn the polarity of the signal imparted to the piezoelectric element 56 is reversed, the element 56 contracts to move the flexible part 18 into the upwardly concave configuration shown in FIG. I as a dashed-dotted line. Because of the connections between the part 18 and the rigid parts 14, 16, the rigid parts I4, 16 counterrotate about the nodal axes 28, 30 into the upwardly divergent attitude shown in FIG. 1 also in dashed-dotted lines. It is apparent that the apertures 24,26 allow flexing of part 18 without physically contacting either of the parts 14, 16.

Because the web 18 is quite long, it can undergo substantial deflections. Consequently, a relatively flexible web produces a resonator of relatively low-frequency. Such -a resonator rotates the parts 14, 16 a substantially greater are than the corresponding parts disclosed in the aforementioned publication and the length of movement of the rigid parts 14, 16 is increased accordingly. Furthermore, there is no loss of Q even when the device is operating with relatively large movement of the parts 14, 16. The basic reason is that the distance between the location 48, 50 is greatest when the web 18 is straight. When the web 18 bends, the natural tendency of the ends thereof is to come together slightly. Since the locations 48, 50 come closer together as the parts 14, 16 move away from the at'rest position, this natural tendency of the web 18 is accommodated with minimum stretching of the web. It will be apparent that these characteristics may prove advantageous in various applications for electromechanical resonators.

A major advantage of this device as compared to the embodiments shown in application Ser. No. 714,22l is that the web 18 can be substantially stiffer. This advantage is more important when a piezoelectric drive is used for the resonator as contrasted to an electromagnetic or other type drive. It is characteristic of piezoelectric drives that they prefer to operate against a relatively stiff member rather than a relatively flexible member for better mechanical impedance matching. With a relatively stiff web 18 as provided by this invention, the mechanical impedance of a piezoelectric wafer can be readily matched against the mechanical impedance of the web 18.

Attention is now directed to FIGS. 3 and 4 where in there is shown a resonator 110 constituting another embodiment of the invention. For purposes of brevity, analogous reference characters are used to indicate analogous elements, most of which will not be specifically discussed. As will be apparent, the major differences between the embodiment of FIGS. 1 and 2 and the embodiment of FIGS. 3 and 4 resides in the location of the flexible part 118 and the resultant changes necessitated in the support means 120.

It will be seen that the rigid parts 114, 116 reside in a plane generally parallel to the base 132. Rather than extending through the rigid parts 114, 116 as in the embodiment of FIGS. I and 2, the third part 118 is disposed in a second plane spaced from the plane defined by the parts 114, 116. The third part 118 is provided with projections 152, 154 which are secured to the parts 114, 116 at locations 148, 150 on opposite sides of the nodal axes 128 130.

Since it IS preferred to have the th|rd part 118 as uncomplicated as possible, the support means extends from only one side of the resonator 110. Consequently, the support means 120 comprises pivot pins 162, 164 encased in a resilient sleeve 166, 168. It will be seen that the pivot pins 162, 164 and the resilient sleeves 166, 168 enable the rigid parts 114, 116 to rotate about the nodal axes 128, 130. It will also be apparent that the third part I18 is arranged to induce counterrotary movement of the rigid parts 114, 116 in a manner substantially identical to that discussed previously.

Attention is now directed to FIGS. 5 and 6 wherein there is shown a resonator 210 constituting another embodiment of the invention. For purposes of brevity, analogous reference characters are used to indicate analogous elements, most of which will not be specifically discussed. The major difference between the embodiment of FIGS. 5 and 6 and the embodiment of FIGS. I and 2 resides in the manner of connecting the web 218 to the rigid parts 214, 216. Rather than welding, soldering or glueing the flexible part 218 to the rigid parts 214, 216, a split-bushing arrangement 270 is provided. The splitbushing arrangement 270 comprises a pair of substantially identical bushing halves 272, 274 which receive the flexible web 218 therebetween. The bushing halves 272, 274 and the third part 218 are press fit or shrink fit into the passageway 224 to provide a force-transmitting connection between the web 218 and the rigid part 214.

The resonator 210 is provided with suitable energizing means, preferably piezoelectric, but not limited thereto, for driving the rigid parts 214, 216 in the same manner as discussed previously with respect to the resonators 10, 110.

While the invention has been shown, illustrated and described in terms of embodiments or modifications which it has assumed in practice, the scope of the invention should not be deemed to be limited by the precise embodiments or modifications herein shown or disclosed.

' I claim:

I. A resonator comprising first and second parts unflexing at a resonant frequency of the resonator;

means supporting the first and second parts in a first plane to enable the parts to rotate about the nodal axes thereof, the nodal axes substantially intersecting the respective centers of gravity of the parts and defining a second plane perpendicular to the first plane;

a third part outside the first plane, flexible at a resonant frequency, connected to the first and second parts at first and second locations to induce counterrotary movement of the first and second parts upon driving of one of the parts, the first and second locations being substantially in the second plane with both nodal axes being between the first and second locations; and

means for driving one of the parts.

2. The resonator of claim 1 wherein the first and second Iocations are disposed on the other edges of the first and second parts respectively.

3. The resonator of claim 1 wherein the first and second parts have substantially equal mass moments of inertia.

4. The resonator of claim 1 wherein the first and second locations are equidistant from the nodal axes. 

1. A resonator comprising first and second parts unflexing at a resonant frequency of the resonator; means supporting the first and second parts in a first plane to enable the parts to rotate about the nodal axes thereof, the nodal axes substantially intersecting the respective centers of gravity of the parts and defining a second plane perpendicular to the first plane; a third part outside the first plane, flexible at a resonant frequency, connected tO the first and second parts at first and second locations to induce counterrotary movement of the first and second parts upon driving of one of the parts, the first and second locations being substantially in the second plane with both nodal axes being between the first and second locations; and means for driving one of the parts.
 2. The resonator of claim 1 wherein the first and second locations are disposed on the other edges of the first and second parts respectively.
 3. The resonator of claim 1 wherein the first and second parts have substantially equal mass moments of inertia.
 4. The resonator of claim 1 wherein the first and second locations are equidistant from the nodal axes. 